Replace "target" with "destination" in M600 (PR#2374)

- Also fix a bug in `M600` where `Z_MAX_ENDSTOP_INVERTING` is being
used as the index into the `destination[AxisEnum]` array.

Marlin/Marlin_main.cpp

@@ -4987,7 +4987,8 @@ inline void gcode_M503() {
         lcd_update();
       #else
         current_position[E_AXIS] += AUTO_FILAMENT_CHANGE_LENGTH;
-        plan_buffer_line(target[X_AXIS],target[Y_AXIS],target[Z_MAX_ENDSTOP_INVERTING],current_position[E_AXIS],AUTO_FILAMENT_CHANGE_FEEDRATE/60,active_extruder);
+        destination[E_AXIS] = current_position[E_AXIS];
+        line_to_destination(AUTO_FILAMENT_CHANGE_FEEDRATE);
         st_synchronize();
       #endif
     } // while(!lcd_clicked)